The barbarian isn't going to just say "I roll athletics" without explaining what they are trying to achieve. Same for persuasion. "I try to convince the mayor we are experienced enough adventurers to assist" is enough to let the GM know what the intention is and give context for the NPC's possible reponse.
A player playing a barbarian isn't expected to deadlift a boulder IRL to prove his character in game is strong.
Why should a player playing a warlock be required to make a persuasive argument IRL to get to prove his character in game is persuasive.
I mean I get a little narration makes the game more fun and diving into the social aspects are just as important as the combat. But We are playing a fantasy game to let people embody whatever fantasy they want and some people just might want to be a lot more charismatic
I feel like you've missed the point of the comment you're replying to
No, a barbarian is not expected to deadlift IRL. But if a barbarian walked into the middle of a situation and declared he was going to solve it with Athletics, without explaining how he was going to do that, he would be met with blank stares. You need to state intent. "I'll use Athletics" is meaningless. "I'll pile up these boulders into a staircase so we can climb over the wall" is a course of action.
Similarly, "I'll use Persuasion" is meaningless. Worse, are the people who just say "I've got proficiency in all the charisma skills, so I'll just use whatever one's most effective" lol. "I'll use my wit and charm to convince the guard that we have been invited to the castle" is a course of action. "I'll use facts and logic to convince the guard that it is in his best interest to allow us into the castle" is a course of action. I don't care if you're charismatic in real life, but if you can't even summarize what you're trying to say, how is the rest of the game world supposed to respond to it? "I'll Persuade them" is only the first half of a sentence.
This makes sense but I think still has a small problem. Someone with good real life people skills is going to be better able to put together a cogent argument, or understand the social dynamics and where to apply pressure.
I don't really know how to solve this. It quickly becomes a "players making these decisions is the whole game" thing.
But I do think that if you have someone who's trying to be a social face without the real life skills, it is okay for the GM to give more hints. Remind players that the knight respects honor and honesty, that the thief is scared and just wants to eat, and so on. Hopefully from there even a shaky player can figure out being honest with the knight is a better move than deception.